An electrophotographic type image-forming device well known in the art has an image-forming unit for transferring developing agent images onto paper or another recording sheet, and a fixing unit for heating the recording sheet to fix the developing agent images to the recording sheet. However, the developer can easily separate from the recording sheet while the sheet is being conveyed along the conveying path from the image-forming unit to the fixing unit.
Further, if the region in which the fixing unit pinches the recording sheet (nip point) is set at a position offset vertically from a direction in which the recording sheet is discharged from the image-forming unit, for example, a trailing edge of the recording sheet in the conveying direction flips upward sharply when the recording sheet is discharged from the image-forming unit.
The impulse of the trailing edge of the recording sheet flipping upward can cause unfixed developing agent to separate from the recording sheet, reducing the quality of the image formed on the recording sheet.
An image forming device disclosed in Japanese patent application publication No. HEI-8-44230 provides entry guides on an entrance side of the fixing unit for preventing the trailing edge of the recording sheet from flipping upward. In order to support various paper sizes, this device has a plurality of entry guides offset from each other in the thickness direction of the recording sheet to support each paper size, the entry guides being configured to hold down both widthwise edges of the recording sheet in an attempt to cope with the sheets of various size.
However, the plurality of entry guides provided for each paper size in this conventional device are offset in the thickness direction of the recording sheet but disposed at the same position in the conveying direction. Accordingly, if the recording sheet conveyed to the fixing unit were bent to form a convex shape protruding in the thickness direction and extending along the longitudinal direction, for example, the entry guides provided for a smaller sheet size than the current recording sheet being conveyed would contact the recording sheet at positions closer to the center of the sheet than the widthwise edges, resulting in the entry guides rubbing against developing agent carried on the recording sheet.
Hence, the developing agent carried on the recording sheet would be separated from the sheet by the rubbing of the entry guides, reducing the quality of the image formed on the recording sheet.